In most chemical reactions the distribution of reaction products (i.e., yield to desired and undesired products) is affected by reaction temperature. In highly exothermic reactions, the heat of reaction must be removed at its rate of formation to maintain a constant temperature of reaction. Many reactions catalyzed by strong acids (e.g., sulfuric, fluorosulfonic, solid polymeric acids and the like) are highly exothermic and require good control of the reaction temperature to obtain high yields of desired products and to minimize side reactions leading to charring and/or formation of tars or other undesired results.
In reactions catalyzed by liquid or gaseous acid catalyst, the catalyst can be molecularly mixed or dispersed with the reactants and the heat of reaction can be removed in conventional heat exchangers in or outside the reaction zone. With good mixing in such fluids reactions, the heat of reaction can be readily distributed from the site of reaction throughout the reaction environment, substantially at its rate of formation, and the bulk temperature and the temperature at the site of reaction can be approximately the same. It is common in highly exothermic decomposition of peroxides exploying sulfuric acid as the catalyst to use a large volume of the sulfuric acid and to meter the reactants into the sulfuric acid to control the extent and rate of heat formation to effect a minimum range of reaction temperature. In addition, it is common to use an inert fluid or excess of one reactant as a heat sink and reaction rate modifier.
In contrast to liquid and gaseous catalysts in fluid or homogeneous systems, solid polymeric catalysts cannot be molecularly dispersed or dissolved in the reactants and the reactants cannot be readily metered to and from an immobile catalyst fixed in a solid polymer matrix. When using a solid polymeric acid catalyst, it is believed that the reaction takes place at the catalyst sites (i.e., small clusters of acidic groups) which are immobilized by the polymer matrix. If the heat of reaction is not removed substantially at the rate of formation, a large increase in temperature could occur at the site resulting in loss of yield of desired products and/or charring of reactants and products which can reduce the utility of the catalyst. The removal of the heat of reaction from the immobilized catalyst sites in a polymer matrix depends on the diffusivity of the reactants, diluents and reaction products in the polymeric matrix and the thermal conductivity (coefficient of heat transfer) of the polymeric matrix. Since methods commonly used to remove heat of reaction and control reaction temperature is substantially homogeneous (liquid or gaseous reactants and catalyst) reaction environments are not readily applicable to reaction environments which are hetereogeneous (solid catalyst and liquid or gaseous reactants and products), attempts have been made to adapt the methods commonly used in the homogeneous systems to the hetereogeneous systems. For example, heat exchanger elements have been immersed in a bed packed with granular ion exchange resins; and granular or powdered ion exchange resins have been slurried with the reactants and diluents and the hetereogeneous mixture passed through a heat exchanger.